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Psoriatic involvement of the nail matrix or bed causing pitting, discoloration, and crumbling; associated with cutaneous psoriasis and psoriatic arthritis.
Nail psoriasis, also known as psoriatic nail dystrophy, occurs when psoriasis affects the nail matrix or nail bed, leading to specific and non-specific clinical changes in the nail. Psoriasis itself is a complex systemic disease involving inflammation and epidermal hyperproliferation.
Nail psoriasis is prevalent in individuals with chronic plaque psoriasis, affecting approximately 90% of them at some point in their lives. While it is more common in adults, with a prevalence of up to 80%, it is less frequently reported in children, occurring in 7 to 13% of cases. When psoriatic nail disease occurs independently without skin or joint involvement, it is observed in about 5 to 10% of adults.
Psoriatic nail disease is considered a potential risk factor for the development of psoriatic arthritis and is often found in association with severe cutaneous psoriasis that persists for a long time.
Nail psoriasis can affect anyone at any age, although there may be a higher incidence among males according to one significant case series. The condition can involve various parts of the nail, such as the nail bed, nail matrix, hyponychium, and nail folds.
Several theories attempt to explain the causes of nail psoriasis. These include the activation of the antimicrobial peptide LL-37 by Candida, the cytokine overflow theory, and increased expression of interleukin (IL)-10 in the affected nail bed compared to downregulation of IL-10 in psoriatic skin lesions. Additionally, psoriasis may be triggered by onychomycosis (fungal infection of the nail) or nail trauma.
Recognised risk factors and associated conditions include:
Nail psoriasis may cause tenderness, pain, altered sense of fine touch, and difficulties with fine motor tasks such as handling shoelaces or buttons.
Clinical signs of nail matrix involvement include:
Clinical signs of nail bed involvement include:
Beau lines (transverse lines and ridges) and nail crumbling are additional clinical signs. Complications can include secondary onychomycosis in the damaged nail plate, psychosocial effects impacting social relationships and work-related activities, and associations with psoriatic arthritis and metabolic syndrome.
Diagnosing nail psoriasis is often based on clinical evaluation, particularly in patients with concurrent psoriatic arthritis and/or cutaneous psoriasis. The Nail Psoriasis Severity Index (NAPSI) can be used to estimate the severity of the condition by scoring clinical signs in each quadrant of the affected nails.
Fungal microscopy and culture of nail clippings should be performed to rule out onychomycosis, which may precede or complicate psoriatic nail dystrophy.
In some cases, a proximal nail matrix biopsy may be necessary to confirm the diagnosis, especially when signs of psoriasis are absent elsewhere or when only one nail is affected and other potential causes must be excluded. However, biopsy carries the risk of causing permanent nail deformities.
Treatment of nail psoriasis is guided by disease severity, the extent of cutaneous or joint involvement, and the impact on quality of life. A comprehensive assessment is recommended to determine the most appropriate approach.
Treatment options include:
Medical attention should be sought when nail changes cause pain, functional impairment, or significant psychosocial distress. Early evaluation is also recommended when nail abnormalities appear in the context of known or suspected psoriasis or psoriatic arthritis, as timely diagnosis and treatment may reduce long-term nail damage and associated complications.
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